Brochure on the New International Calibration Standards

Product Price Quantity $ Total SFr Total
Order Form
DCHA-Iso, ICS-I2 $100
Name
DCHA-Rho, ICS-R2 $100
Tetra, ICS-T2 $100
Co./Inst.
DCHA-Hexa, ICS-H1 $100
ICE-2 CHF 250
Address
GRAND TOTAL
No credit cards or checks accepted.
Charge for shipping CHF 15.
Postal Code City
Payment to Labor Veritas:
Country
Zürcher Kantonalbank, CH-8010 Zurich
Account no. 1100-00524.060
Telephone
Labor Veritas, Zürich, Engimattstrasse 11
Postfach 353
CH-8027 Zürich, Switzerland.
Fax
Phone: +41 (44) 283 29 30
Fax: +41 (44) 201 42 49
E-mail: admin@laborveritas.ch
Web site: www.laborveritas.ch
E-mail
International
Calibration
Standards for
HPLC Analysis
of Isomerized
α-Acids
Current from May 07
New International Calibration
Standards for HPLC Analysis of
Isomerized α-Acids
In 1998, the ASBC, EBC, IoB (now IBD), and BCOJ
began working together toward the creation and international
adoption of a single set of HPLC standards for
use in the quantitative determination of isomerized and
reduced-isomerized α-acids in hop products and in beer.
The resultant International Calibration Standards (ICS)
were produced, analyzed, and verified for the benefit of
the brewing industry by the International Subcommittee
for Isomerized Hop α-Acids Standards and first released
in 2001.
The purity of each standard was determined using various
HPLC procedures, elemental analysis, and other methods.
The standards were later reanalyzed, using an isocratic
version of EBC Method 7.8, following which the total
concentrations of the major isomerized α-acids were
determined. Samples of the standards showed excellent
stability even after two years at room temperature,
although freezer storage is strongly recommended. New
DCHA-Iso, DCHA-Rho, and Tetra standards (ICS-I2,
ICS-R2 and ICS-T2) are now prepared, replacing the
originals that are now available only while stocks last.
General
■ These standards are deemed to have the reported composition
only when used according to the accompanying
instructions for storage, handling and use, especially
including chromatography by the recommended, isocratic
variation of Method EBC 7.8 (now issued as EBC 7.9).
■ Compared to these standards, samples of hop products,
and the worts and beers made from them, may contain
substantially different proportions of the constituent
isomerized α-acids. However, these latter compounds
are believed to all have quite similar extinction coefficients
at 270 nm in the mobile phase of the recommended
method, hence the standards are considered
suitable for use in quantifying isomerized α-acids in all
unknown samples.
■ Detailed information pertaining to each standard, plus
full instruction for use, is available on request and is supplied
with each purchase, including: two chromatograms
of a single analysis that illustrate (1) the major peaks
upon which the calibration must be based and (2) the
minor peaks that are also present in the preparation.
The spectra obtained from a photo-diode array (PDA)
detector scanning at the peak maxima of all these peaks
are also included.
Limitations
■ Most HPLC methods will not reliably separate all cisand
trans-isomers of the three major homologs (co-,
n- & ad-) of a given type of isomerized α-acid. These
standards are therefore recommended primarily for the
determination of the total content of isomerized α-acids
of the stated type in an unknown sample, though it may
often be possible to concurrently determine the cohumulone
homologs content.
■ In some HPLC elution solvents it may be expected
that the extinction coefficients of the different isomers
and homologs are not at all similar, leading to substantial
errors in quantification of an unknown sample.
Especially, this may be the case if the detector is set to
an inappropriate wavelength.
■ Where mixtures of different types of iso-α-acids are
present, they may not be fully resolved by some HPLC
methods, leading to errors of identification and quantitative
evaluation.
Purchasing
These Iso standards can be purchased, at the
equivalent price, from:
1. Labor Veritas, Zürich, Engimattstrasse 11
Postfach 353
CH-8027 Zürich, Switzerland.
Phone: +41 (44) 283 29 30
Fax: +41 (44) 201 42 49
E-mail: admin@laborveritas.ch
Web site: www.laborveritas.ch
2. American Society of Brewing Chemists
(ASBC): 3340 Pilot Knob Road
St. Paul, MN 55121, USA.
Phone: +1.651.454.7250
Fax: +1.651.454.0766
E-mail: asbc@scisoc.org
Web site: www.asbcnet.org
Orders from Europe and Africa should be directed
to Labor Veritas, from North and South America to
ASBC, from elsewhere to either seller. LV reserves the
right to limit the number of vials of each
standard purchased.
#7697EBC-5/07

DCHA-Iso, ICS-I2
DCHA-Rho, ICS-R2
Tetra, ICS-T2
DCHA-Hexa, ICS-H1
ICS-I2 is a purified preparation of the dicyclohexylamine
salts of trans-iso-α-acids. It is deemed to have a total
iso-α-acids content of 64.3% (w/w), though this figure takes
into account only the major forms of the iso-α-acids that
are present: trans-isocohumulone, trans-isohumulone and
trans-isoadhumulone. (N.B. Worts and beers brewed with
hops, hop extracts, pellets and all commercial “Iso” products
invariably also contain substantial proportions of the
corresponding cis-iso-α-acids - see User’s Guide supplied
with the standard).
If you are using the recommended method, expect the area
of the trans-isocohumulone peak to be about 47.5% of the
total peak area of all of the compounds included in the
calibration. (Caution: This may not be the case for methods
that use other mobile phases, or for measurement at different
wavelengths).
ICS-I2 replaces ICS-I1. The new standard has been
cross-checked against the old and will give similar results.
ICS-R2 is a purified preparation of the dicyclohexylamine salts
of cis-ρ-iso-α-acids. This standard is deemed to have a total
ρ-iso-α-acids content of 65.3% (w/w), though this figure takes
into account only the major forms of the ρ-iso-α-acids that are
present: two cis-ρ-isocohumulones, two cis-ρ-isohumulones and
two cis-ρ-isoadhumulones. (N.B. Commercial “Rho” products
typically contain a significant proportion of a trans-ρ-isohumulone
isomer - see User’s Guide supplied with the standard).
If you are using the recommended method, expect the combined
area of the cis-ρ-isocohumulones peaks* to be about
14.5% of the total peak area of all of the compounds included
in the calibration. (Caution: This may not be the case for
methods that use other mobile phases, or for measurement at
different wavelengths).
ICS-R2 replaces ICS-R1. The new standard has been
cross-checked against the old and has an essentially identical
response factor per unit of total cis-ρ-iso-α-acids.
* The supplied chromatogram shows two peaks, corresponding to
the two cis forms of this particular iso-α-acid. However, it is not
known which peak corresponds to which of the two forms shown
below. (The same is also true for the ρ-isohumulones peaks).
ICS-T2 is a purified preparation containing both cis- and
trans-isomers of the tetrahydroisocohumulones,
tetrahydroisohumulones and tetrahydroisoadhumulones.
In respect of these six isomers it is deemed to have a total
tetrahydroiso-α-acids content of 99.4% (w/w).
If you are using the recommended method, expect the
(combined) area of the tetrahydroisocohumulones
peak(s)* to be about 39% of the total peak area of all of
the compounds included in the calibration. (Caution: This
may not be the case for methods that use other mobile
phases, or for measurement at different wavelengths).
ICS-T2 replaces ICS-T1. The new standard has a much
higher cis:trans ratio than the old and this may result in a
small reduction (typically 1 - 2% relative) to the value
obtained for “total Tetra” in an unknown sample.
* The supplied chromatogram shows only one peak.
However, it is often found that the two isomers of
tetrahydroisocohumulone are partially resolved.
ICS-H1 is a purified preparation of the dicyclohexylamine
salts of cis-hexahydroiso-α-acids. It is deemed to have a
total hexahydroiso-a-acids content of 65.7% (w/w), though
this figure takes into account only the major forms of hexahydroiso-α-acids
that are present: two cis-hexahydroisocohumulones,
two cis-hexahydroisohumulones and two
cis-hexahydroisoadhumulones.
If you are using the recommended method, expect the combined
areas of the cis-hexahydroisocohumulones peaks* to
be about 53% of the total peak area of all of the compounds
included in the calibration. (Caution: This may not be the
case for methods that use other mobile phases, or for
measurement at different wavelengths).
* The supplied chromatogram shows two peaks, corresponding
to the two cis forms of this particular iso-α-acid.
However, it is not known which peak corresponds to which
of the two forms shown above. (The same is also true for the
ρ-isohumulones peaks).
Structures of DCHA-Iso-alpha-acids
Structures of DCHA-rho-Iso-alpha-acids
Structures of Tetrahydroiso-alpha-acids
Structures of DCHA-Hexahydroiso-alpha-acids
H
HO
O
O
O
O -
H 2 N +
DCHA - trans-Isocohumulone
C 32 H 51 NO 5
(mw 529.751)
H
HO
HO
O
O -
H
O
R
H 2 N +
cis-
H
HO
O
O
O
OH
R
H
HO
HO
O
O -
H
O
R
H 2 N +
O
H
HO
O
O
O -
H 2 N +
DCHA - trans-Isohumulone
C 33 H 53 NO 5
(mw 543.778)
H
HO
HO
O
O -
H
O
R
H 2 N +
DCHA-Rho, ICS-R2
(contains two cis forms of
each rho-iso-α-acid)
trans-
O
H
HO
O
O
OH
R
Tetra, ICS-T2
(contains both cis & trans forms of
tetrahydroiso-α-acids)
H
HO
HO
O
O -
H
O
R
H 2 N +
DCHA-Hexa, ICS-H1
(contains two cis forms of
each hexahydroiso-α-acid)
O
O
H
HO
O
O -
H 2 N +
DCHA - trans-Isoadhumulone
C 33 H 53 NO 5
(mw 543.778)
DCHA-rho-isocohumulones
C 32 H 53 NO 5
(mw 531.765)
DCHA-rho-isohumulones
& isoadhumulones
C 33 H 55 NO 5
(mw 545.791)
Tetrahydroisocohumulones
C 20 H 32 O 5
(mw 352.464)
Tetrahydroisohumulones &
Tetrahydroisoadhumulones
C 21 H 34 O 5
(mw 366.490)
DCHA-hexahydroisocohumulones
C 32 H 57 NO 5
(mw 535.796)
DCHA-hexahydroisohumulones
& isoadhumulones
C 33 H 59 NO 5
(mw 549.823)